The Crab Nebula Radio Pulsar: Is it Different?

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AWARD NO: AST-0607492PI: Timothy HankinsINSTITUTION: New Mexico Institute of Mining and TechnologyTITLE: The Crab Nebula Radio Pulsar: Is it Different?ABSTRACTIt is thought that the radio emissions from pulsar magnetospheres are ruled by plasmaelectrodynamics in a rotating system where the magnetic field is strong enough forquantum effects to matter and the induced electric field is strong enough to acceleratecharges to high Lorentz factors. Yet theoretical models of the physical conditions anddetails of the emission mechanism have gone largely unchallenged because of thedifficulty testing them against traditional pulsar observations. However, because modelsdiverge in their predictions for short timescales, the PIs have been pursuing high timeresolution observations of the Crab Nebula pulsar. New data acquisition systemsdeveloped for this purpose have detected nanosecond long radio bursts from the Crab'sMain Pulse region and the fundamental entities creating the coherent radio emission. Thetime and frequency characteristics of these "nanoshots" are consistent with a strongplasma turbulence model. However, subsequent observations of a second emitting region,the Interpulse, revealed dramatically different time and frequency signatures indicatingsubstantially different physical conditions which are difficult to explain.As the Crab pulsar is unusual because of its young age, a similar study of a small set(five) of bright pulsars will be undertaken. These pulsars have been chosen to representthe range of likely conditions in other pulsars and the observations will reveal whetherthe type of emission from the Crab is typical of the general pulsar population. For theCrab itself, intensity and polarization fluctuations on microsecond timescales, as well astime averaged polarization signatures, will be connected to the physical conditions in theemission region by additional theoretical modeling performed by the PIs. Theoreticalmodels of the Interpulse emission will also be critically studied to determine which, ifany, existing model can explain these observations.Graduate and undergraduate students will be directly involved in all aspects of this work- from constructing and maintaining the data collection systems to developing thenumerical codes for modeling and analysis. Beyond the laboratory, some of the researchtools used here will be made available for teaching in local classes and the scientificresults incorporated into web-based teaching materials (in addition to dissemination inthe professional literature). The state-of-the-art acquisition systems, which will beimproved as part of this work, will be made available to the radio astronomy communityon a collaborative basis. The data acquisition and control software developed by the PIsis directly applicable to, and available for use in lightning research by the AtmosphericPhysics group at New Mexico Tech.